Domestic Hot Water Distribution Device

ABSTRACT

A domestic hot water distribution device includes a supply water inlet, a waste water collector and means for heating the supply water in order to produce domestic hot water from the heat contained in the waste waters The heating means include thermo-electric modules laid out for operating heat transfer from the waste waters to the supply water to be heated.

BACKGROUND

The present invention generally relates to devices for distributing domestic hot water integrating heat recovery from the heat of waste waters.

Devices for distributing hot water integrating a heat recovery device as the one described for example in document U.S. Pat. No. 4,821,793, are known in the prior art. This document discloses a shower comprising a water-water coil exchanger for operating energy recovery from waste water. As a counterpart, this system notably has the drawback of being bulky and not very efficient for recovering a large amount of heat.

Moreover, document US2009/0242005 discloses a dishwasher equipped with Peltier modules for heating the cleaning water of the dishwasher. This system is not adapted to the production of domestic hot water because of the relevant temperature ranges. Indeed, in a dishwasher, the water is heated to 85° C., which is totally incompatible with the use for a shower for example. The result of this is a significant loss in efficiency and cooling of the water produced by this system would even have to be provided in order to use the water for domestic uses.

Document FR 2 486 060 describes a facility for treating waste waters of a dwelling with a heat recovery unit.

SUMMARY

An object of the present invention is to overcome the drawbacks of the above-mentioned documents of the prior art and in particular, to first of all propose a compact device for producing domestic hot water with a significant efficiency in energy recovery.

For this, a first aspect of the invention relates to a device for distributing domestic hot water comprising a supply water inlet, a waste water collector and means for heating the supply water in order to produce domestic hot water from the heat contained in the waste waters, characterized in that the heating means include thermo-electric modules laid out for performing heat transfer from the waste waters to the supply water to be heated. The device according to the invention provides a compact and economical solution for recovering heat in waste waters by using thermo-electric modules as a heat pump. The domestic hot water is delivered at a temperature comprised between 35° C. and 60° C.

Advantageously, the heating means comprise at least one first heat exchanger laid out for operating, from waste waters towards the supply water, a first heat transfer resulting in a temperature difference of less than a predetermined difference, and the thermo-electric modules are laid out downstream from the first heat exchanger in a second heat exchanger operating a second heat transfer from the waste waters to the supply water. The present invention suitably uses a first heat exchanger for generating predetermined favorable conditions to the operation of the second exchanger including thermo-electric modules. The heat exchanges are concomitant with the distribution of hot water for recovering the heat in the loop. In other words, the distributed hot water is recovered and forms the waste waters which pass into the first exchanger laid out for transferring, during the hot water distribution, a portion of the heat contained in the waste waters towards the supply water. Thus, the first exchanger carries out first heating of the supply water, simultaneously with the distribution of hot water, in order to deliver to the second exchanger comprising the thermo-electric modules a water supply and waste waters having a reduced temperature difference. This reduced temperature difference gives the possibility of placing the thermo-electric modules of the second exchanger in an advantageous operating range as a heat pump consuming very little electric current, in order to carry out the second heat transfer. The cold supply water is exclusively heated with these two heat exchangers, before being distributed as domestic hot water.

Advantageously, the first heat exchanger delivers to the second heat exchanger waste waters and a supply water having a maximum temperature difference of 20° C. Ideally, the temperature difference between the waste waters and the supply water is a maximum of 15° C. The applicant noticed that this temperature range was particularly advantageous for obtaining operation of the thermo-electric modules with a COP of more than 1.

Advantageously, the thermo-electric modules are defined with a maximum operating temperature difference and the first heat exchanger delivers to the second heat exchanger waste waters and supply water having a rated temperature difference of less than 20% of the maximum operating temperature difference. The applicant noticed that this temperature range was particularly advantageous for obtaining operation of the thermo-electric modules with a COP greater than 1.

Advantageously, the thermo-electric modules are defined with a maximum electric current of use and the thermo-electric modules are powered with a rated power supply current of less than 20% of the maximum current of use. Ideally, the rated power supply current is 15% of the maximum current of use. The applicant noticed that this range of use was particularly advantageous for obtaining economical operation of the thermo-electric modules with a coefficient of performance (COP) of more than 1. It may also be noted that the energy losses through the Joule effect in the thermo-electric modules will be transmitted to the supply water, which further increases the coefficient of performance.

A particularly interesting embodiment consists in that the first heat exchanger is laid out for delivering to the second heat exchanger waste waters and supply water having a temperature difference of less than the predetermined difference for placing the thermo-electric modules in an operating range with a coefficient of performance (COP) greater than 1. The first exchanger according to this application is specially designed for operating a first heat exchange, while delivering waste waters and supply water having a maximum temperature difference which determines a particular operation of the thermo-electric modules. Indeed, the latter, used as a heat pump and if they are subject to a maximum temperature difference, will operate in a particularly advantageous operating range with a coefficient of performance (COP) greater than 1. In other words, such a COP, representing the energy provided to the supply water by the thermo-electric modules divided by the electric energy provided to the thermo-electric modules, if it is greater than 1, indicates that the thermo-electric modules provide the supply water with more energy than they actually consume. The device becomes more economical to use than a solution with a water reserve conventionally heated with electric resistors.

Very advantageously, the first heat exchanger is a water-water exchanger. This solution is economical.

Advantageously, the second heat exchanger comprises: a waste water inlet and a waste water outlet connected through at least one waste water conduit, a supply water inlet and a supply water outlet connected through at least one supply water conduit. The thermo-electric modules having a cold face and a hot face are laid out between a wall of the waste water conduit and a wall of the supply water conduit. The cold face being laid out for capturing the heat of the waste water and the hot face being laid out for delivering heat to the supply water. The waste water and supply water conduits are laid out for minimizing the temperature differences between the hot faces and the cold faces along the second exchanger.

The layout of the conduits for minimizing the temperature differences along the second exchanger gives the possibility of remaining as long as possible in the preferred range for using the thermo-electric modules.

Advantageously, the waste water and supply water conduits are laid out for operating a counter-current circulation in the second exchanger. With this application it is possible to ensure a constant temperature difference along the second exchanger comprising the thermo-electric modules, for maintaining them in the preferred range of use.

Advantageously, the device delivers supply water at a final temperature and comprises means for adjusting the final temperature of the supply water, capable of controlling the thermo-electric modules for adjusting the final temperature of the supply water. The adjustment means according to the invention comprise a man-machine interface allowing the user to define the final temperature of the supply water, and depending on this final temperature, the adjustment means power the thermo-electric modules with suitable current in order to obtain the desired final temperature.

A second aspect of the invention is a shower comprising a device for distributing domestic hot water according to the first aspect of the invention. The integration of the device according to the first aspect of the invention in a shower is very favorable, since this compact device is quite suitable for operating without storing any hot water, since it only produces hot water when the shower is used. Next, by means of the use of the thermo-electric modules in a particular operating range generated by the first exchanger, the energy yield is correct with a COP greater than I. It should be noted that it is possible to integrate the device according to the first aspect of the invention into a wash basin or a sink, where discharge of the waste waters is concomitant with the provision of hot water.

Another aspect of the invention relates to a method for distributing domestic hot water comprising the steps consisting of: distributing domestic hot water, recovering this hot water for forming waste waters, operating in a first heat exchanger simultaneously with the distribution of hot water, from the waste waters and to the supply water, a first heat transfer resulting in a temperature difference of less than a predetermined difference, between the waste waters and the supply water at the outlet of the first heat exchanger, operating, downstream from the first heat exchanger, and in a second heat exchanger with thermo-electric modules, a second heat transfer from the waste waters to the supply water simultaneously with the hot water distribution, and distributing the thereby heated supply water as domestic hot water.

The method according to the invention allows economical heating in devices for distributing hot water for which the waste waters are recovered, simultaneously with the distribution, such as for example a shower or a wash basin without storage of water for example.

Advantageously, a preliminary step for initiating the system is carried out at the beginning of the hot water distribution and consisting of heating the supply water by the Joule effect with the thermo-electric modules.

Advantageously, the predetermined difference is of a maximum of 20° C.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will become more clearly apparent upon reading the detailed description which follows of an embodiment of the invention given as a by no means limiting example and illustrated by the appended drawings, wherein FIG. 1 represents a shower equipped with a device according to the invention.

DETAILED DESCRIPTION

FIG. 1 illustrates a shower with a device for distributing hot water comprising a first heat exchanger 10 and a second heat exchanger 20. The shower includes a shower head and a pan for recovering the water projected by the shower head. The waste waters are discharged through an outlet 12 and then enter the first heat exchanger 10. The latter for example consists of a reservoir fed by the outlet 12 of the shower pan and in which is laid out a helical tube. The tube is supplied with cold water through a supply inlet 11. First heating of the cold water is operated in the first exchanger 10 by transfer of a portion of the heat contained in the waste waters towards the cold water. Typically, the waste waters have a temperature comprised between 30 and 40° C. and the cold water between 5 and 15° C. The first exchanger is laid out so that at the outlet of the first exchanger, the temperature difference between the waste waters at point 14 and the supply water at point 13 is less than a predetermined value, 20° C. for example, which corresponds to a predetermined operating range of the second thermo-electric heat exchanger where its coefficient of performance will be greater than 1.

The second exchanger 20 includes a plurality of thermo-electric modules, (also called Peltier modules) 25 inserted between a waste water conduit 27 and a supply water conduit 26. The thermo-electric modules 25 include two main faces, one being the cold face, the other the hot face. The hot faces of each thermo-electric module are laid out in direct contact with the supply water conduit 26 and the cold faces are laid out in direct contact with the waste water conduit 27. The conduits 27 and 26 are laid out so that they operate at a counter-current, in order to keep a temperature difference as constant as possible between the waste waters and the supply water. Further, by electrically powering the thermo-electric modules, the latter will operate like a heat pump. Ideally, the power supply will be accomplished with a power of less than a predetermined fraction (20% for example) of the maximum power of the thermo-electric modules, so as to be located in an advantageous range with a coefficient of performance of greater than 1. The layout of the first exchanger gives the possibility of obtaining a temperature difference between the waste waters and the supply water entering the second exchanger placing the second exchanger in an operating range where its coefficient of performance will be greater than 1.

It will be understood that various modifications and/or obvious improvements for one skilled in the art may be made to the different embodiments of the invention described in the present description without departing from the scope of the invention as defined by the appended claims. In particular, reference is made to a water-water exchanger; an exchanger with plates, with tubes, with U-shaped tubes, with a horizontal or vertical, spiral or block tubular manifold may be contemplated. Moreover, the use of the device according to the invention in any hot water distribution device which includes discharge of hot waste waters containing energy, continuous and concomitant with the hot water supply may also be contemplated. 

1. A device for distributing domestic hot water comprising: a supply water inlet, a waste water collector and a heater configured to heat the supply water to produce domestic hot water from the heat contained in the waste waters, the heater comprising at least a first heat exchanger configured to heat supply water from the supply water inlet to provide a temperature difference of less than a predetermined difference and a second heat exchanger disposed downstream from the first heat exchanger that includes thermo-electric modules to further heat the supply water.
 2. The domestic hot water distribution device according to claim 1, wherein the first heat exchanger configured to deliver to the second heat exchanger waste water and supply water having a temperature difference of a maximum of 20° C.
 3. The domestic hot water distribution device according to claim 1, wherein the thermo-electric modules are defined with a maximum electric current of use and are configured to be powered with a rated power supply current of less than 20% of the maximum current of use.
 4. The domestic hot water distribution device according to claim 1, wherein the first heat exchanger is configured to deliver to the second heat exchanger waste water and supply water having a temperature difference of less than the predetermined difference for placing the thermo-electric modules in an operating range with a coefficient of performance (COP) greater than
 1. 5. The domestic hot water distribution device according to claim 1, wherein the first heat exchanger is a water-water exchanger.
 6. The domestic hot water distribution device according to claim 1, wherein the second heat exchanger comprises: a waste water inlet and a waste water outlet connected through at least one waste water conduit, a supply water inlet and a supply water outlet connected through at least one supply water conduit, thermo-electric modules including a cold face and a hot face disposed between a wall of the waste water conduit and a wall of the supply water conduit, the cold face being disposed to capture heat of the waste waters and the hot face being disposed to deliver heat to the supply water, wherein the waste water and the supply water conduits are are configured to minimize the temperature differences between the hot face and the cold face along the second heat exchanger.
 7. The domestic hot water distribution device according to claim 6, wherein the waste water and supply water conduits are configure to operate with counter-current circulation.
 8. A shower comprising a domestic hot water distribution device according to claim
 1. 9. A method for distributing domestic hot water comprising: distributing domestic hot water, recovering the domestic hot water for forming waste waters, operating in a first heat exchanger simultaneously with the hot water distribution, a first heat transfer from the waste waters and to the supply water to provide a temperature difference of less than a predetermined difference, between the waste waters and the supply water at the outlet of the first heat exchanger, operating, downstream from the first heat exchanger and in a second heat exchanger with thermo-electric modules, a second heat transfer from the wasted waters to the supply water simultaneously with the hot water distribution, distributing the heated supply water as domestic hot water.
 10. The method according to claim 9, wherein a preliminary step for initiating the system is carried out at the beginning of the distribution of hot water, includes heating the supply water with thermo-electric modules.
 11. The method according to claim 9, wherein the predetermined difference is a maximum of 20° C.
 12. A shower comprising a domestic hot water distribution device according to claim
 7. 